The present invention relates to a conveyance means of a sorter which is combined with an image forming apparatus such as a copier or printer, and by which recording sheets delivered from the apparatus are conveyed and sorted.
Generally, the sorter is combined with an image forming apparatus 100 as shown in FIG. 4, and recording sheets 101 delivered from the apparatus 100 are sequentially conveyed and accommodated in a plurality of bins 51 provided in the sorter 10 by a conveyance means and, for example, a switching gate provided in the conveyance section of the sorter. Then, the recording sheets are separated into a specified number of groups.
In a fixed bin sorter, there are two types of sheet distributing methods, one is a method by which recording sheets are distributed into bins by a switching gate, and the other is a method by which the recording sheets are distributed into bins by a distributor (an indexer). The method by the indexer is superior to the other method in cost, and recently is mainly used.
In the method in which the sheets are distributed by the distributor, as the typical prior art of methods to convey sheets, there are two examples as follows.
One is the method in which the sheet is sandwiched between a thin plate spring and a conveyance belt, and then conveyed. The other is the method in which the recording sheet is pressed by a sheet guide, such as a Mylar sheet guide, and a conveyance belt, and then conveyed.
Referring to the drawings, the foregoing two methods will be described as follows.
In the method in which the recording sheets are distributed to bins by switching gates, the switching gates 15a, 15b, . . . 15n are provided along a conveyance belt 12, and bins 51a, 51b, . . . 51n corresponding to the switching gates are provided as shown in FIG. 5. The recording sheets are conveyed while being sandwiched between the conveyance belt 12 and conveyance rollers 14. For example, in the case where the recording sheet is sent to the bin 51b, the switching gate 15b is turned to the position of 15b1 in FIG. 5 by a mechanism not shown in the drawing, and the recording sheet is sent to the bin 51b in the arrowed direction.
That is, the switching gates 15 are provided one by one corresponding to each of bins 51, and when the switching gates sequentially turn their directions, the recording sheets are sequentially sent to the bins 51 corresponding to each of switching gates 15. As described above, in the foregoing method, the number of parts is large, and the structure becomes complicated.
On the other hand, in the method in which the recording sheet is distributed to each bin by the distributor, as shown in FIG. 6 or FIG. 7, the distributor is moved in the upper and lower directions along the conveyance belt 12 by a mechanism not shown in the drawings.
The recording sheet is sandwiched between the conveyance belt 12 and a thin plate spring 35, or between the conveyance belt 12 and the sheet for guide 35a such as a Mylar sheet guide, or pressed by them, and then, conveyed. The recording sheets are successively sent to each of bins 51 in the arrowed direction by the distributor 21 which stops at each position corresponding to bins 51.
That is, in the distributor 21, a moving member 34 having a couple of delivery rollers 30 can be moved in the upper and the lower directions by a mechanism not shown in the drawings, and can be successively stopped at the corresponding bins 51. The moving member 34 has a receiving port 23a and a delivery port 23b. The recording sheets are sent to the bins as follows: the recording sheets are sandwiched between the conveyance belt 12 and thin plate spring 35, or between the conveyance belt 12 and the sheet guide such as a Mylar sheet guide, or pressed by them for conveyance; the conveyed sheets are sent from the receiving port 23a to the distributor 21; and then the recording sheets are conveyed successively from the delivery port 23b to bins 51 corresponding to the position of the stopped distributor 21.
Further, there are two sheet conveyance methods in the above-described sheet distribution method, and the difference between them will be described as follows.
That is, in the method in which the recording sheet is sandwiched between the conveyance belt 12 and the thin plate spring 35 for conveyance, there are the following advantages in which: as shown in FIG. 6, the structure of the moving member 34 is simple; and the receiving port 23a and the delivery port 23b are necessarily formed by the delivery roller 30 and the conveyance belt 12 even when the receiving port 23a and the delivery port 23b are not newly or separately provided. On the other hand, the foregoing method has the following disadvantage in which: there is a problem in sheet conveyance property because the sheet conveyance force is given by the spring force of the thin plate spring. In the sheet conveyance method in which the sheet is pressed by the sheet guide 35a, such as a Mylar sheet guide, and the conveyance belt 12, its structure is simple as shown in FIG. 7, however, a countermeasure to prevent static electricity is necessary because the sheet guide is formed by the Mylar sheet, and there is a problem in maintenance.
As described above, there are various problems in the conventional methods, and therefore, a sufficient method can not be obtained.
That is, in the switching gate method, the number of parts is large, therefore the structure is complicated, the cost is high, and accordingly there is a possibility that problems are easily caused. Further, as a result of the foregoing, maintenance properties are deteriorated, and it is difficult to handle the apparatus.
Further, in the method using a distributor, when the thin plate spring is used, the conveyance force of the sheet depends on the spring properties of the thin plate spring, and therefore there are problems that the absolute value of the spring force is low, and the conveyance properties of the sheet are unstable.
In another method using the distributor in which a Mylar sheet is used, the sheet guide is formed by the Mylar sheet, so that the guide is apt to be electrostatically charged, and therefore, a discharging means should be especially considered. Since the conveyance belt is pressed from its inside, there is a case where it is necessary to remove the belt pressing device when jamming occurs. Therefore, it is necessary to provide a removal means by which the device can be easily removed, and the structure becomes complicated.
The present invention has been proposed to solve the foregoing problems. The object of the present invention is to provide a low cost sorter having the following advantages: a distributor method is provided, the cost of which is lower than that of the switching gate method; the conveyance force of the sheet is increased so that the sheet can be stably conveyed; the sheet is not electrostatically charged during conveyance; it is not necessary to provide a complicated structure to remove the pressing force by which the conveyance belt is pressed from the inside; and a sorter in which the structure is simple, the probability of failure is low, and the cost is low, can be provided.